Lubricant handling method and apparatus for refrigeration systems



Oct. 4, 1966 MCDONELL 3,276,215

P. LUBRICANT HANDLING METHOD AND APPARATUS FOR REFRIGERATION SYSTEMS Filed March 26, 1964 INVENTOR. PERRY I M DoNELL BY J jg fl olzmi Y 91mm.

ATTORNEYS 3,276,215 LUBRICANT HANDLING METHOD AND APPARA- TUS FOR REFRIGERATION SYSTEMS Perry T. McDonell, 1131 Portland Ave. SE., Atlanta, Ga. Filed Mar. 26, 1964, Ser. No. 354,905 2 Claims. (Cl. 62-84) This invention relates to refrigeration systems and more particularly to apparatus for preventing damage by refrigerant in a liquid state to compressors used in refrigeration systems.

Refrigeration systems customarily return refrigerant to the compressor or compressors of the system in a gaseous state for compression by one or more of the compressors. However, portions of the refrigerant commonly used in refrigeration systems are frequently changed from a gaseous state to a liquid state when the refrigeration system is undergoing automatic or hot gas defrosting or when components of the refrigeration system are malfunctioning. If these portions of refrigerant in a liquid state enter the compressor or compressors of the refrigeration system, the compressor or compressors are seriously damaged and may even break up with sufiicient force to severely injure nearby personnel.

Numerous previous efforts have been made to prevent the possible damage to equipment and personnel caused by refrigerant in a liquid state entering the compressor or compressors of a refrigeration system. Some of these previous efforts have resulted in apparatus which simply traps refrigerant in a liquid state before the refrigerant in a liquid state can enter the compressor or compressors of a refrigeration system. This apparatus makes no provision for changing the refrigerant back to its gaseous state from its liquid state and as a result there is a decrease in the amount of refrigerant available for operation of the refrigeration system.

Other previous efforts to prevent injury to equipment and personnel by a refrigerant in a liquid state entering the compressor or compressors of a refrigeration system have attempted to avoid this loss of refrigerant available for the operation of a refrigeration system by trapping the refrigerant in a liquid state and returning this refrigerant to a gaseous state. These efforts have generally utilized a liquid trap in which the heat of compressed refrigerant in a gaseous state or warm liquid refrigerant is used to vaporized the refrigerant in a liquid state.

The compressed refrigerant must subsequently be used in the condenser and the difficulty with apparatus of this type is that since the compressed refrigerant must pass through the trap in a coil or similar arrangement, a leak in the coil or similar arrangement will cause some of the compressed refrigerant to simply pass from the compressor or compressors of the refrigeration system through the trap and back to the compressor or compressors of the refrigeration system. This reduces the amount of refrigerant that circulates through the entire system and causes overheating of the compressor or compressors. It also tends to equalize the pressures in the system so as to produce an efliciency loss within the system.

Thus, apparatus of this type must be carefully manufactured using components suited only for use in apparatus of this type so as to avoid leaks. This has made apparatus of this type relatively expensive to manufacture. Moreover, in an effort to insure reliability, apparatus of this type has customarily been manufactured as a single integral structure which is difiicult to maintain.

A further difiiculty with apparatus which vaporizes a refrigerant in a liquid state in a liquid trap is that the compressed refrigerant in a gaseous state must be circulated through the coil or similar arrangement in the liquid trap,

v United States Patent O 1 3,276,215 Patented Oct. 4, 1966 thus requiring expensive controls and reducing the efficiency of the refrigeration system as a whole.

Previous refrigeration systems, especially those using ammonia as a refrigerant, have not been able to defrost all of the evaporators of the system at once. Only part of the evaporators may be defrosted at a time since the heat from the other evaporators which are refrigerating is required to defrost the evaporators which are not refrigating. If all of the evaporators are located in the same enclosure, moisture from the defrosting evaporators travels to the refrigerating evaporators causing overicing on these evaporators and reducing not only the defrosting efficiency of the system but also the overall efiiciency of the system.

The apparatus for preventing damage by liquid refrigerant to compressors used in refrigeration systems disclosed herein overcomes these and other problems and difficulties associated with refrigeration systems. The apparatus utilizes standard, easily obtainable, and relatively inexpensive to manufacture components to separate both lubricating oil and refrigerant in a liquid state from a refrigerant in a gaseous state and to return the refrigerant in a liquid state to a compressor of the refrigeration system in a gaseous state and the lubricating oil to a reservoir in a compressor for lubrication purposes.

The apparatus comprises a liquid trap in which ref-rigerant in a liquid state and lubricating oil are trapped and separated from refrigerant in a gaseous state and a vaporization member in which the refrigerant in a liquid state is changed from a liquid state to a gaseous state by exhaust heat from the condenser of the refrigeration system and in which lubricating oil accumulates to be returned to the compressor or compressors of the refrigeration system for lubrication purposes.

Gravity or a pump transfers the trapped refrigerant in a liquid state and the lubricating oil from the liquid trap to the vaporization member for vaporization and the pressure diiference created between the liquid trap and the vaporization member when refrigerant in a liquid state is vaporized transfers vaporized refrigerant from the vaporization member to the liquid trap. Thus, none of the energy that the refrigeration system uses to circulate refrigerant is used as transfer means for the apparatus disclosed herein. As a result, the apparatus does not adversely affect the efiiciency of the refrigeration system with which the apparatus is used.

Moreover, the possibility of the compressed refrigerant passing only through the liquid trap and a compressor of the refrigeration system is avoided since no compressed refrigerant passes through a coil in the liquid trap.

The separation of refrigerant in a liquid state and lubricating oil from refrigerant in a gaseous state and the changing of refrigerant in a liquid state to a gaseous state is accomplished by the apparatus dis-closed herein in a continuous and fully automatic manner. The return of lubricating oil to the compressor or compressors of a refrigeration system for lubrication purposes is accomplished either manually or in a fully automatic manner utilizing a throttling valve or orifice in conjunction with a solenoid valve which opens to return the lubricating oil to the compressor or compressors of a refrigeration system when the compressors are operating. Thus, the apparatus disclosed herein is not only relatively inexpensive to manufacture and maintain, but it is also extremely reliable and durable so that it may be operated for extended periods of time without attention.

The present invention also allows all of the evaporators of a refrigeration system to be defrosted at once. By recirculating the refrigerant vaporized by the present invention through the evaporators of the system, the additional heat needed from refrigerating evaporators to defrost the evaporators of the system is avoided.

These and other features and advantages of the present invention will be more clearly understood from the following detailed description and the accompanying drawings in which like characters of reference designate corresponding parts in all figures and in which:

FIG. 1 is a schematic presentation of the embodiment of the invention disclosed herein used in a refrigeration system having a single compressor.

FIG. 2 is a schematic presentation of the embodiment of the invention disclosed herein used in a refrigeration system having a plurality of compressors and evaponators.

FIG. 3 is a partial perspective view of the vaporization coil used in the embodiment of the present invention shown in FIGS. 1 and 2.

FIG. 4 is a cross-sectional view of the liquid trap used in the embodiment of the present invention shown in FIGS. 1 and 2.

These figures and the following detailed description disclose a specific embodiment of the present invention but the invention is not limited to the details disclosed since it may be embodied in other equivalent forms.

The embodiment of the present invention comprises generally a liquid trap and a vaporization coil connected in a conventional refrigeration system having a compressor 14, an evaporator 12, and a condenser 19. The liquid trap 10 is connected in the refrigeration system between the evaporator 12 and the compressor 14 and communicates with the vaporization coil 15 so that refrigerant in a liquid state that is trapped by the liquid trap 10 is transferred to the vaporization coil 15 where it is vaporized and then transferred back to the liquid tra 10.

The liquid trap 10 is of a known type that separates a liquid from a gas. As a mixture of the refrigerant in a liquid state, refrigerant in a gaseous state, and lubricating oil flows into the liquid trap 10 through a refrigerant return pipe 11 connecting the evaporator 12 and the liquid trap 10, the refrigerant in a gaseous state moves to the upper portion of the liquid trap 10, and the refrigerant in a liquid state and the lubricating oil settle to the lower portion of the liquid trap 10.

The upper portion of the liquid trap 10 communicates with the suction inlet of the compressor 14 through a gas return pipe 16, thus allowing the refrigerant in a gaseous state to flow to the compressor 14 to be compressed by the compressor 14 from which the refrigerant flows through the tubing 50 for recycling through the refrigeration system. The lower portion of the liquid trap 10 communicates with the lowermost coils of the vaporization coil 15 through a liquid transfer pipe 18 which is inclined so that the force of gravity causes the refrigerant in a liquid state and the lubricating oil collected in the lower portion of the liquid trap 10 to flow from the liquid trap 10 to the vaporization coil 15 substantially as fast as the mixture entering the liquid trap 10 is separated.

The vaporization coil 15 is of known type such as that used for evaporative condensers and is positioned in the refrigeration system so that the liquid transfer pipe 18 is inclined as described above. The condenser 19 is also positioned so that the hot air exhaust 2th from the condenser 19 flows through the vaporization coil 15. Thus, as refrigerant in the liquid state and the lubricating oil enter the lowermost coils of the vaporization coil 15, heat from the hot air exhaust 20 vaporizes the refrigerant in a liquid state. The vaporized refrigerant creates a higher pressure in the vaporization coil 15 than is present in the liquid trap 10. This pressure forces the vaporized refrigerant through the vaporization coil 15 and back to the liquid trap 10 through a gas transfer pipe 21 connecting the uppermost coils of the vaporization coil 15 and the upper portion of the liquid trap 10. The gas transfer pipe 21 is inclined so that the vaporized refrigerant will rise to the liquid trap 10 whereas any refrigerant in a liquid state will drain back into the vaporization coil 15 to be vaporized. It will be understood that any vaporized refrigerant that condenses while on the way from the vaporization coil 15 to the liquid trap 10 merely drains back into the vaporization coil 15 under the force of gravity to be vaporized again. Thus, principally refrigerant in a gaseous form reaches the liquid trap 10 from the vaporization coil 15. However, if some refrigerant in a liquid state is carried along the gas transfer pipe 21 between bubbles of vaporized refrigerant and forced into the liquid trap 10, the liquid trap 10 separates the refrigerant in a liquid state from the refrigerant in agaseous state and returns the refrigerant in a liquid state to the vaporization coil 15 for vaporization.

The lubricating oil that enters the lowermost coils of the vaporization coil 15 with the refrigerant in a liquid state is not vaporized by the heat from the hot air exhaust 20 as is the refrigerant since the vaporization temperature of the lubricating oil is above the temperature of the hot air exhaust 20. Therefore, as the refrigerant in a liquid state is vaporized, the lubricating oil accumulates in the lowermost coils of the vaporization coil 15.

An oil return pipe 22 connects the lowermost coils of the vaporization coil 15 with the oil reservoir in the compressor 14, and a normally closed solenoid 24 and an orifice 27 are imposed in the oil return pipe 22. The solenoid valve 24 is connected to an activating source of known type so that it closes the oil return pipe 22 when the compressor 14 is not operating and opens the oil return pipe 22 when the compressor 14 is operating. Since most of the heavier liquid entering the vaporization coil 15 is lubricating oil, that portion of the liquid passing into the oil return pipe 22 when the compressor 14 is operating is principally lubricating oil. The orifice 27 serves to prevent high flow rates of liquid through the oil return pipe 22 thereby permitting only a small portion of the total quantity of liquid entering the vaporization coil 15 to return to the oil reservoir in the compressor 14.

When the compressor 14 is operating, the lubricating oil accumulates in the lowermost coils of the vaporization coil 15 and is returned to the oil reservoir in the compressor 14 by the oil return pipe 22 and the orifice 27 along with small amounts of refrigerant in a liquid state. A vent pipe 26 connects the oil reservoir of the compressor 14 with the suction inlet of the compressor 14. Thus, any refrigerant in a liquid state returning to the oil reservoir in the compressor 14 is vaporized due to the heat of the compressor 14 and is transferred to the cornpression cylinder of the compressor 14 to be circulated through the refrigeration system by the suction of the compressor 14.

When the compressor 14 is not operating, the solenoid valve 24 closes the oil return pipe 22 and prevents any liquid from flowing into the oil reservoir of the compressor 14. Since the vaporization coil 15 is customarily located so that refrigerant in a liquid state is not vaporized when the refrigeration system is not operating, the refrigerant in the liquid trap 10 and the vaporization coil 15 accumulated when the system is not operating is prevented from flooding the oil reservoir in the compressor 14 by the solenoid valve 24 closing the oil return pipe 22. Each time the compressor 14 is started and stopped the solenoid valve 24 opens and closes the 011 return pipe 22, thus the above procedure is repeated each time the system starts and stops operation.

The use of the present invention in a multiple refrigeration system having a plurality of compressors 14, a condenser 19, and a plurality of evaporators 12 is shown in FIG. 2. The refrigerant return pipe 11 connects the evaporators 12 and the liquid trap 10 through an evaporator manifold 31 connecting the evaporators 12. Refrigerant in a liquid state and lubricating oil are trapped by the liquid trap 10, and transferred to the vaporization coil 15 in the same manner as heretofore described. The vaporization coil 15 vaporizes the refrigerant in a liquid stateand transfers the vaporized refrigerant back to the liquid trap while accumulating the lubrication oil as heretofore described.

The gas return pipe 16 connects the liquid trap 10 with a compressor manifold 30 which distributes the refrigerant in a gaseous state equally between the suction inlets of the compressors 14. The oil return pipe 22 connects the lowermost coils of the vaporization coil with an oil reservoir manifold 32 which distributes the lubricating oil returned by the oil return pipe 22 equally between the compressors 14.

Operation It will now be understood that as a mixture of refrigerant in a gaseous state, refrigerant in a liquid state, and lubricating oil exit the evaporator 12 of the refrigeration system shown in FIG. 1 during a hot gas defrosting cycle or some malfunction of a component of the refrigeration system it is separated by the liquid trap 10 so that the refrigerant in a gaseous state rises to the upper portion of the liquid trap 10 and the refrigerant in a liquid state along with the lubricating oil settles to the lower portion of the liquid trap 10.

The refrigerant in a gaseous state is forced from the liquid trap 10 through the gas return pipe 16 to the compressor 14 by the suction pressure created by the compressor 14, and the refrigerant in a liquid state along with the lubricating oil trapped by the liquid trap 10 is transferred by gravity through the liquid transfer pipe 18 to the lowermost coils of the vaporization coil 15.

Heat from the hot air exhaust 20 vaporizes the refrigerant in a liquid state in the lowermost coils of the vaporization coil 15; thus raising the pressure in the vaporization coil 15 above that in the liquid trap 10. The pressure difference between the vaporization coil 15 and the liquid trap 10 causes the vaporized refrigerant to rise through the vaporization coil 15 and return to the liquid trap 10 where the suction from the compressor 14 causes the vaporized refrigerant to be forced into the compressor 14.

The lubricating oil is accumulated in the lowermost coils of the vaporization coil 15 as the refrigerant in a liquid state is vaporized by the heat from the condenser 19, and since the refrigerant in a liquid state is vaporized substantially as fast as it enters the vaporization coil 15, principally lubricating oil is returned to the oil reservoir in the compressor 14 via the oil return pipe 22 and the orifice 27 when the compressor 14 is operating.

When the compressor 14 stops operation the solenoid valve 24 is closed preventing any of the lubricating oil and refrigerant in a liquid state that enters the vaporization coil 15 from the liquid trap 10 or any of the vaporized refrigerant condensed in the vaporization coil 15 from returning to the oil reservoir in the compressor 14 When the compressor 14 is not operating.

In a multiple refrigeration system, the mixture of refrigerant in a liquid state, refrigerant in a gaseous state, and lubricating oil is collected by the evaporator manifold 31 from the evaporators 12 and transferred to the liquid trap -10 through the refrigerant return pipe 11.

The refrigerant in a liquid state is vaporized in the vaporization coil 15 as explained above, and transferred to the liquid trap 10. The refrigerant in a gaseous state is transferred to the compressor manifold 30 through the gas return pipe 16 which distributes the refrigerant to the compressors 14 equally.

The accumulated lubricating oil is transferred as explained above through the oil return pipe 22 to the oil reservoir manifold 32 which distributes the 'lubricating oil to the oil reservoirs of the compressors 14 equally.

It will be obvious to those skilled in the art that many variations may be made in the embodiments here chosen for the purpose of illustrating the present invention without departing from the scope thereof as defined by the appended claims.

What is claimed as invention is:

1. A refrigeration system comprising a compressor; a condenser; an evaporator; a refrigerant; trapping means operatively positioned between the compressor and the evaporator for separating refrigerant in a gaseous state from the refrigerant in a liquid state and lubricating oil; a coil operatively connected to said trapping means so as to receive refrigerant in a liquid state and lubricating oil from said trapping means, said coil being positioned in the hot air exhaust from the condenser; means for conducting refrigerant in a gaseous state from the coil to the trapping means; means for selectively draining lubricating oil at a controlled rate of flow from the coil to an oil reservoir in the compressor; and means for allowing refrigerant in a gaseous state to pass from the oil reservoir to a compression cylinder of the compressor.

2. A method providing only refrigerant in a gaseous state to the compressor in a refrigeration system having a compressor, a condenser, and an evaporator, said method comprising the steps of separating refrigerant in a liquid state and lubricating oil from refrigerant in a gaseous state between the evaporator and the compressor, moving the refrigerant in a liquid state obtained by said separation into the hot air exhaust from the conenser by gravity, heating the refrigerant in a liquid state with the heat of the hot air exhaust from the condenser until said refrigerant changes from liquid state to gaseous state, moving refrigerant in a gaseous state from the hot air exhaust of the condenser to the evaporator, moving the lubricating oil and refrigerant in a liquid state trapped therein to the oil reservoir of the compressor by gravity, vaporizing refrigerant in a liquid state in the oil reservoir of the compressor by the heat of the compressor, and

allowing refrigerant in a gaseous state to escape from the oil reservoir of the compressor to a compression cylinder of the compressor.

References Cited by the Examiner UNITED STATES PATENTS 1,760,195 5/1930 'Gunn 62ll3 XR 2,121,253 6/1938 McGuffey 62471 X 2,461,342 2/1949 Obreiter 6283 2,705,405 4/1955 Uhlman 62474 2,900,801 8/1959 Honegger 62471 X ROBERT A. OLEARY, Primary Examiner.

W. E. WAYNER, Assistant Examiner. 

2. A METHOD PROVIDING ONLY REFRIGERANT IN A GASEOUS STATE TO THE COMPRESSOR IN A REFRIGERATION SYSTEM HAVING A COMPRESSOR, A CONDENSER, AND AN EVAPORATOR, SAID METHOD COMPRISING THE STEPS OF SEPARATING REFRIGERANT IN A LIQUID STATE AND LUBRICATING OIL FROM REFRIGERANT IN A GASEOUS STATE BETWEEN THE EVAPORATOR AND THE COMPRESSOR, MOVING THE REFRIGERANT IN A LIQUID STATE OBTAINED BY SAID SEPARATION INTO THE HOT AIR EXHAUST FROM THE CONDENSER BY GRAVITY, HEATING THE REFRIGERANT IN A LIQUID STATE WITH THE HEAT OF THE HOT AIR EXHAUST FROM THE CONDENSER UNTIL SAID REFRIGERANT CHANGES FROM LIQUID STATE TO GASEOUS 